Verbesina species. At this stage hard to tell which species. Texas has 9 species, and I'm only familiar with virginica, alternifolia, and encelioides. Winged petioles.

Hmm, well it's getting ready to bloom soon...so maybe that will help narrow it down further?

Looks like Frostweed. It's a very prolific self seeder in my garden. I'm out of room for anymore. They grow fast and bloom the first year. Great for pollinators. Verbesina virginica most likely. You have more Verbesina species down there that I'm not familiar with.

There are 2 other white flowered Verbesina in Texas, V. microptera and V. walteri. All 3 white flowered species have very different flowers.

OK yea it bloomed and is definitely Frostweed (Verbesina virginica?)!